1. Field
This invention relates to power tongs for coupling and uncoupling pipes or tubes used for the operation of removing underground fluids to the surface; more particularly, the power tong relates to power tongs for coupling and uncoupling single or multi-concentric pipes or tubing used in the production of underground fluids such as oil and gas and water.
2. State of the Art
Numerous techniques have been developed in the used of power tongs for gripping and rotating links of pipe or tubing sometimes referred to as joints. Generally, power tongs comprise a body or housing, a rotary mechanism mounted in said body to impart rotation at least one active jaw to engage the pipe with other active or passive jaws that sufficiently engage the pipe so that the jaws rotate with the rotary mechanism relative to the body of the power tongs to couple or uncouple one joint from another joint held stationary. Most of the power tongs provide cams to move the active jaws into gripping arrangements with the pipe to be rotated. Once the joints have been coupled or uncoupled, the power tong generally must be disengaged from surrounding the pipe such that the uncoupled joint may be removed or a new joint positioned for coupling to the pipeline string. Various methods of withdrawing the power tong have been proposed by providing a tong such as described in U.S. Pat. No. 3,023,651 to EM Wallace illustrated with two segments being connected to the main segments by pivots. The tong requires a latch to secure the pivotal segments around the pipe to be coupled or uncoupled.
The deficiency in power tongs with only one active jaw, the active jaw must be dismounted and remounted on the opposite side of the rotary requiring a different camming, thus consuming time. In other power tongs, two cam members are provided, which permits rotation in either direction from a neutral position.
Another problem with prior power tongs is the limited range of pipe sizes that can be used in which proper gripping action is achieved without surface damage to the pipe. Other tong arrangements have provided for replacing cam members to meet the requirements of satisfactorily gripping the pipe to avoid damaging the surface.
The present invention provides a power tong for coupling and uncoupling tubular member including relative large diameters and relative small diameters whether in a concentric or not configuration, wherein a housing or frame support three chordal segments, which are similar to the shape of the moon halfway between the first quarter and fully phases, with the arcs being toothed and the chordal border mounting gripping elements, which may be adjustable by providing spacers behind the gripping elements designed for gripping relatively large pipe and behind gripping elements designed for gripping relatively small pipe. The chordal segments include a master segment linked to slave segments at each side of the master segment. The segments are rotated in one direction for moving the gripping elements into engagement with and uncoupling the pipe, or in the opposite direction for coupling. The chordal segments, mounted between an upper and a lower slotted plates for rotation relative to the housing, are driven by a chain drive, which imparts pivoting of the chordal segments to engage a pipe or tubular member and then rotate the chordal segment, the slotted plates and pipe or tubular member and permits removal of the tool from surrounding the tubing string when the chordal segments, are in the neutral position and aligned with the slotted plates, whereby the power tong may be positioned around a tubing string or removed form the tubing string as necessary.
Further advantages of the present invention include the chordal sections being mounted to a rotary member, which when the gripping elements on the chordal segments engage a tubular member initiates rotation of the rotary mechanism and continues for sufficient revolutions to either uncouple or couple a pipe joint from the rest of a string of pipes being held stationary.
To insure that the chordal segments are in a neutral position when backed off from gripping the pipe, a stop lug or pin is provided mounted on the master segment which engages the linkage between the master segment and the slave segment allowing the rotary mechanism to rotate in the opposite direction to the neutral position.
It is an additional feature of the invention that the gripping elements may be adjusted by spacers to engage different diameters of tubing to afford the same even gripping pressure on the tubing regardless of the diameter. Likewise, the angle of the gripping element faces may be changed by removing one series of gripping elements and replacing them with another. Further features permit coupling or uncoupling an entire string of pipe without re-centering the tongs about the pipe string the so long as the greatest diameter of the pipe string is less then the diameter of the opening for surrounding pipe to be coupled or uncoupled. Also, multiple concentric strings of pipe my be coupled by providing the appropriate size gripping elements in the master and slave chordal segments by coupling the smaller pipe then backing off the chordal segments, moving the larger pipe in a position over the smaller joint engaging the gripping elements with this larger pipe and coupling it to the same diameter pipe. The action is repeated until the inner and outer pipes have been appropriately coupled. In achieving the coupling of the different sizes of pipe, spacers may be used behind the gripping elements as well as the gripping elements may be changed so that the face of the gripping elements may be provided at a different angle for the particular pipe being engaged. The arrangement provides a quick release set screw to retain the gripping elements, with or without spacers, in the appropriate position on the chordal segments.
In the chain drive arrangement, the chordal segments are driven until they lock up against the pipe; then the chordal segments being part of the rotary table, the entire segments driven by the chain drive rotate with the rotary table to fully couple or uncouple the pipes. Since the toothed arc of the leading chordal segment will be rotated out of engagement with the chain across the cavities in the frames while the trailing chordal segment will vacate the region adjacent the frame cavity, two chain carriers are provided mounted from the rotary mechanism engage the chain drive, thus preventing lost tension on chain. Further, to keep tension on the chain, two spring loaded idler sprockets are provided in the travel path of the chain.